A medium carbon steel sheet has been widely used as a material for a chain, a gear, a clutch, a saw, a blade, and the like. To make the material into a product, a process of shaping the material into a predetermined shape and hardening the material using a heat treatment such as quenching and tempering is commonly performed. Therefore, both workability and hardenability are required for medium carbon steel sheets. Particularly, in recent years, a working technology has been developed, wherein a shaping method in which compression working and tension working are performed at the same time, and the working ratio is higher compared to the related art has been adopted. Therefore, it is necessary for a medium carbon steel sheet to have shaping properties capable of enduring hard working. Furthermore, according to recent demands for energy conservation, there are movements to change the quenching and tempering process from a furnace heating type in the related art to a high-frequency heating type. To adapt the changing needs, it is necessary to develop a medium carbon steel sheet that is soft before cold working, endures working during the cold working, and has an excellent hardenability after high-frequency heating (hereinafter, referred to as high-frequency hardenability. In addition, quenching after high-frequency heating is referred to simply as “high-frequency quenching).